/*
 * acm1048.c
 *
 *  Created on: 20 Mar 2010
 *      Author: xuxu
 */
#include<stdio.h>
int main()
{
	double monin,total;
	int i;
	total=0;
	for(i=0;i<12;i++)
	{
		scanf("%lf",&monin);
		total+=monin;
	}
	printf("$%.2lf",total/12);
}
